The United Kingdom's National Archives has unveiled a new slew of UFO-related documents, including papers describing Winston Churchill's cover-up of a UFO sighting during World War II. The Prime Minister massively soft-pedaled the encounter to avoid public hysteria.

Among the declassified documents is a letter from 1999 in which the grandson of one of Churchill's bodyguards claims that the Prime Minister withheld reports of an RAF aircraft's run-in with a UFO:

* The Western Isles incident, when a loud explosion was reported in the sky over the Atlantic in the Outer Hebrides.

* The 14-minutes of "missing" film relating to the Blue Streak missile test launch in 1964, believed by some to show a "spaceman".

* A gambler from Leeds who held a 100-1 bet on alien life being discovered before the end of the 20th Century, and who approached the government for evidence to support his claim after the bookmakers refused to pay out. The MoD said it was open-minded about extra-terrestrial life but had no evidence of its existence.